class_docstr: Tree node of a dendrogram.
code: def leaves(self, values=True):
      if self._children:
          leaves = []
          for child in self._children:
              leaves.extend(child.leaves(values))
          return leaves
      elif values:
          return [self._value]
      else:
          return [self]
  
imports: import copy
  from abc import abstractmethod
  from math import sqrt
  from sys import stdout
  from nltk.cluster.api import ClusterI
label_desc: Use image node_id 2 for calling the _DendrogramNode obj's underlying member method code with example usage: obj.leaves(values) and returns: leaves, list, list